The process for high pressure extraction has been known for many years from many publications. In high pressure extraction, the solvent properties of compressed gases or gas mixtures are utilized in many ways to dissolve and separate components from solid-like raw materials. The separated components are obtained as tracts or the raw material per se is purified as a result of the separation. Industrially realized applications of the process of high pressure extraction are, for example, the production of hops extract and the production of caffeine-free coffee. As example, U.S. Pat. No. 4,561,452 is mentioned which shows a process for the production of low nicotine tobacco.
High pressure extraction installation in the simplest case consist of an extractor and a separator through which the gaseous solvent in circulated. In the extractor, the gas under high pressure, mostly above-critical pressure, flows through the solid-like raw material and in this process is charged with certain organic content substances. These content substances can be selectively dissolved as a function of the set extraction conditions. The dissolved components leave the extractor together with the solvent flow and are separated in the separator. The separation can be achieved by various measure, namely, by pressure and temperature changed, by absorbers or wash solutions or by adding other gases which reduce the solvating power of the gaseous solvent.
From this basic process of high pressure extraction, many variations were developed employed to adapt the process to certain objectives or for economical optimization. Examples are the application of gas mixtures to attain higher selectivities and the application of several separation autoclaves operating at various pressure levels for the production of fractionated extracts.
All known variations have in common that the extraction process is operated exclusively as a circulation process. The extractors as well as the separators are, therefore, continuously included in the solvent circulation. Time-consuming extraction processes, in particular, therefore require high energy expenses and considerable investment for the layout of pumps. This applies, in particular, when the solvating power of the solvent is reduced by the addition of foreign gases to increase the selectivity.